Self-propelled cleaner and method of controlling the same

ABSTRACT

In a cleaner, it is determined whether or not a remaining volume of a battery is equal to or more than a sum of a battery volume required for returning to a position of a battery charger and a predetermined allowance value. When the remaining volume of the battery is determined to be equal to or more than the sum, a control unit supplies a current during 80% of a predetermined time length to a left drive wheel motor and a right drive wheel motor and halts the supply of the current during 20% of the predetermined time length. When the remaining volume of the battery is determined to be below the sum, the control unit supplies the current during 40% of the predetermined time length to the left drive wheel motor and the right drive wheel motor and halts the supply of the current during 60% of the predetermined time length.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a self-propelled cleaner and a methodof controlling the cleaner. More particularly, the present inventionrelates to a self-propelled cleaner for cleaning a space to be cleanedthrough an autonomous travel, and a method of controlling the cleaner.

2. Description of the Background Art

Conventionally, a self-propelled cleaner capable of storing a travelingpath has been available. Further, in an example of the self-propelledcleaner, a traveling distance between a present position and a chargingposition is calculated, a remaining volume of a battery is detected, andthe cleaner is controlled so that it returns to a charging stand whenthe remaining volume of the battery approximates to a volume of thebattery required for the traveling from the present position to thecharging position, as recited in Japanese Patent Laying-Open Nos. 7-8428and 2002-318620.

The foregoing documents relating to the conventional technology recitedthat the “control for returning to the charging stand” was such acontrol that a destination of the traveling was changed to the chargingstand, wherein there was no discussion on a traveling mode after thedestination was changed to the charging stand.

SUMMARY OF THE INVENTION

The present invention has been implemented in order to deal with theforegoing disadvantage, and an object thereof is to enable aself-propelled cleaner to unfailingly return to a charging stand evenwhen the remaining volume of a battery is lessened to some extent.

A self-propelled cleaner according to an aspect of the present inventionincludes a traveling unit, a traveling drive unit for driving thetraveling unit and allowing the cleaner to autonomously travel, asuction unit for implementing a suction operation for cleaning, a powersupply for supplying the traveling drive unit and the suction unit witha current, a control unit for controlling modes of supplying the currentto the traveling drive unit and the suction unit from the power supply,and a voltage detecting unit for detecting a voltage of the powersupply. Herein, when a voltage value detected by the voltage detectingunit is below a predetermined value, the control unit makes a length oftime for supplying the traveling drive unit with the current within apredetermined length of time shorter than a length of time when thevoltage value detected by the voltage detecting unit is equal to or morethan the predetermined value.

A self-propelled cleaner according to another aspect of the presentinvention includes a traveling unit, a traveling drive unit for drivingthe traveling unit and allowing the cleaner to autonomously travel, asuction unit for implementing a suction operation for cleaning, a powersupply for supplying the traveling drive unit and the suction unit witha current, and a control unit for controlling modes of supplying thecurrent to the traveling drive unit and the suction unit from the powersupply. Herein, the control unit supplies the traveling drive unit witha current value lower than a current value demanded by the suction unitfor its suction operation in order to drive the traveling unit.

A method of controlling a self-propelled cleaner according to thepresent invention is a method of controlling a self-propelled cleanerincluding a traveling unit, a traveling drive unit for driving thetraveling unit and allowing the cleaner to autonomously travel, asuction unit for implementing a suction operation for cleaning, and apower supply for supplying the traveling drive unit and the suction unitwith a current. Herein, the method includes a step of detecting avoltage of the power supply, a step of determining whether or not thevoltage of the power supply is equal to or more than a predeterminedvalue, a step of supplying the traveling drive unit with the currentduring a first length of time within a predetermined time length whenthe voltage of the power supply is equal to or more than thepredetermined value, and a step of supplying the traveling drive unitwith the current during a second length of time shorter than the firstlength of time within the predetermined time length when the voltage ofthe power supply is below the predetermined value.

According to the present invention, when the voltage value of the powersupply is below the predetermined value, the current value required forthe traveling can be controlled. Accordingly, the self-propelled cleanercan reliably return to the charging stand even when the remaining volumeof the power supply is lessened to some extent because the cleaner cantravel in a relatively long length of time.

Further, according to the present invention, the current value requiredfor the traveling is set to the value lower than the current valuerequired for the suction and thereby controlled. Accordingly, theself-propelled cleaner can reliably return to the charging stand evenwhen the remaining volume of the power supply is lessened to some extentbecause the cleaner can travel in a relatively long length of time.

A self-propelled cleaner according to the present invention includes atraveling unit, a traveling drive unit for driving the traveling unitand allowing the cleaner to autonomously travel, a suction unit forimplementing a suction operation for cleaning, a power supply forsupplying the traveling drive unit and the suction unit with a current,a control unit for controlling modes of supplying the current to thetraveling drive unit and the suction unit from the power supply, and avoltage detecting unit for detecting a voltage of the power supply. Thecurrent value necessarily supplied to the traveling drive unit fordriving the traveling unit is lower than the current value necessarilysupplied to the suction unit for its suction operation, and the controlunit, when the voltage value detected by the voltage detecting unit isbelow the predetermined value, shortens the length of time for supplythe traveling drive unit with the current within the predeterminedlength of time in comparison with the case of the voltage value beingequal to or more than the predetermined value. The power supply isrechargeable when it is connected to the battery charger. A pathcalculating section for calculating a path from the present position ofthe power supply to the battery charger is further included. Thepredetermined value is based on a voltage value required for travelingthe path from the present position of the power supply to the batterycharger calculated by the path calculating section.

The foregoing and other objects, features, aspects and advantages of thepresent invention will become more apparent from the following detaileddescription of the present invention when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a self-propelled cleaner according to anembodiment of the present invention;

FIG. 2 shows a lower surface of the cleaner of FIG. 1;

FIG. 3 is a sectional view of the cleaner taken along line III-III ofFIG. 1;

FIG. 4 is a block diagram of the cleaner of FIG. 1 and a battery chargerfor charging a battery of the cleaner;

FIGS. 5A and 5B are illustrations of modes of controlling a voltage withrespect to a left drive wheel motor and a right drive wheel motor of thecleaner of FIG. 1;

FIGS. 6A and 6B are illustrations of modes of controlling a current withrespect to the left drive wheel motor and the right drive wheel motor ofthe cleaner shown in FIG. 1;

FIG. 7 is a perspective view of a modification of the cleaner of FIG. 1;

FIG. 8 shows a lower surface of the cleaner of FIG. 7; and

FIG. 9 is a block diagram of the cleaner of FIG. 7 and a battery chargerfor charging a battery of the cleaner.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, an embodiment of the present invention will be describedreferring to the drawings.

Referring to FIG. 1, a cleaner 1, whose exterior part is covered with aouter jacket 2, has a substantially disk shape. On outer jacket 2,antennas 18 and 19, a display unit 24, an input unit 25, proximitysensors 14 to 17, and distance-measuring sensors 11 to 13 are provided.Input unit 25 is constituted of a switch and the like and used by a userwhen he/she inputs information to cleaner 1. A surface, which is nearlyvertical in part, is formed in a frontal surface of outer jacket 2, anda camera 20 is disposed on the surface. Below camera 20 is provided anLED (Light Emitting Diode) 35 for supplementing an illumination whenphotographing is carried out by means of camera 20. In a forwarddirection of cleaner 1 and on a lower side of outer jacket 2, sidebrushes 73 are each provided on right and left.

Next, referring to FIG. 2, the sensors installed in cleaner 1 will bedescribed. In FIG. 2, some of the components, such as side brushes 73and LED 35, are not shown.

Cleaner 1 is further provided with an acceleration sensor 23 and aterrestrial magnetism sensor 24. As seen in FIGS. 1 and 2, proximitysensors 14 to 17 are each disposed in front, rear, right and left ofcleaner 1.

Referring to FIG. 3, an internal structure of cleaner 1 will bedescribed. Support plates 2A and 2B are disposed inside of outer jacket2. A control basement 40, in which parts for controlling an operation ofcleaner 1 are packaged, is disposed on support plate 2A. In asubstantially central portion of cleaner 1, a main brush 72 for rakingup dust on a floor surface by rotation is disposed. A main brush motor62 is driven and a driving force resulting therefrom is conveyed via agear 63A, which rotates main brush 72. The dust raked up by main brush72 is collected in a dust-collecting cup (not shown). When a suctionmotor 64 is driven, the raked-up dust is guided into the dust-collectingcup via a nozzle (not shown). Suction motor 64 is disposed on supportplate 2B.

In FIG. 3, a left drive wheel 70 is shown. Cleaner 1 is provided withdrive wheels, which are left drive wheel 70 and a right drive wheel (notshown), each disposed on right and left. Cleaner 1 starts to travel whenthe two drive wheels are driven. Left drive wheel 70 is driven inresponse to a left drive wheel motor 60 being driven. Cleaner 1 isfurther provided with auxiliary wheels respectively disposed behind theright and left drive wheels. An auxiliary wheel 79 is provided behindleft drive wheel 70. At a rearmost part of cleaner 1, a dust sensor 34is provided. Dust sensor 34 is a unit including an infrared-ray sensorserving to detect an amount of dust on the floor surface.

Cleaner 1 operates using a rechargeable battery (battery 30 which willbe described later) as a power source.

Referring to FIG. 4, constitutions of cleaner 1 and a battery charger 9for charging the battery will be described.

Cleaner 1 includes battery 30.

Battery charger 9 includes a control unit 90 for generally controllingan operation of battery charger 9, a charging unit 91 for controlling acharging operation with respect to battery 30, a power supply circuit 92connected to battery 30 by a connector or the like and thereby servingto charge battery 30, and a supersonic wave generating unit 93 foroutputting a supersonic-wave signal. Battery charger 9 is supplied withan alternating-current power supply such as a commercial-use powersupply. Power supply circuit 92 converts alternative-current powersupplied by battery charger 9 into direct-current power to therebycharge battery 30. A remaining volume detecting unit 31 for detecting avoltage of battery 30 is connected to battery 30.

Cleaner 1 includes a control unit 10 for generally controlling theoperation of cleaner 1. Control unit 10 includes a position/directionidentifying section 41, a suction control section 42, a brush controlsection 43, a traveling control section 44, a traveling path calculatingsection 45 and a determining section 46.

Control unit 10 is connected to motor control units 51 to 54. Motorcontrol unit 51 controls the drives of left drive wheel motor 60 andright drive wheel motor 61. Left drive wheel motor 60 serves to driveleft drive wheel 70, while right drive wheel motor 61 serves to drivethe right drive wheel. Motor control unit 52 controls the drive of mainbrush motor 62. Motor control unit 53 controls the drive of a side brushmotor 63. Side brush motor 63 serves to drive side brush 73. Motorcontrol unit 54 controls the drive of suction motor 64.

The information inputted to input unit 25 is inputted to control unit10. Further, detection outputs of remaining volume detecting unit 31,dust sensor 34, distance-measuring sensors 11 to 13, proximity sensors14 to 17, terrestrial magnetism sensor 22 and acceleration sensor 23 areinputted to control unit 10.

Further, image data captured by camera 20 is inputted to control unit10, and control unit 10 can reference time counted by a timer 21provided in the cleaner and further control operations of display unit24 and LED 35.

Cleaner 1 is further provided with a communication unit 26 forcommunicating with other devices. Control unit 10 can communicate withother devices via communication unit 26 and antennas 18 and 19.

Cleaner 1 is further provided with an auxiliary battery 32 and a solarcell 33. In cleaner 1, auxiliary battery 32 can be charged utilizinglight irradiated on solar cell 33. Cleaner 1 can also be operated bymeans of power supplied by auxiliary battery 32.

Control unit 10 is connected to a memory unit 27. In memory unit 27, amap information storing section 28, in which positional coordinatesrepresenting a size and a shape of each of a plurality of rooms asoperational areas of cleaner 1, map information of entrance/exitcoordinates of the each room and cleaning pattern information and thelike of the each room are stored, is formed.

Position/direction identifying section 41 calculates a position, amoving amount and a moving direction of cleaner 1 based on detectionoutputs of terrestrial magnetism sensor 22 and acceleration sensor 23and modes of driving left drive wheel motor 60 and right drive wheelmotor 61 by motor control unit 51 and identifies a present position anda traveling direction of cleaner 1 from the calculated position, movingamount, moving direction and map information stored in map informationstoring section 28.

Traveling path calculating section 45 calculates a traveling path fromthe present position identified by position/direction identifyingsection 41 to a position of battery charger 9 (more specifically,position stored in map information storing section 28, at which battery30 is connected to the above-mentioned connector and thereby charged bypower supply circuit 92).

Determining section 46 calculates a battery volume (voltage value)required for cleaner 1 to return to the position of battery charger 9 inaccordance with the traveling path calculated by traveling pathcalculating section 45 and compares the calculated battery volume to aremaining volume (voltage value) of battery 30 detected by remainingvolume detecting unit 31 to thereby determine whether or not cleaner 1is allowed to travel back to the position of battery charger 9. Morespecifically, determining section 46 renders the decision that cleaner 1travels to return to battery charger 9 when the remaining volume of theof battery 30 falls below a sum of the battery volume required forreturning to the position of battery charger 9 and a predeterminedallowance volume.

Traveling control section 44 controls motor control unit 51 based on thepresent position identified by position/direction identifying section 41and the map information stored in map information storing section 28.Cleaner 1 is allowed to autonomously travel because traveling controlsection 44 can control operations of the right and left drive wheelsbased on the present position and the map information.

Suction control section 42 and brush control section 43 respectivelydrive motor control unit 54 and motor control unit 53 during a periodwhen the cleaning should be carried out based on the present positionand the map information stored in map information storing section 28.

As described, cleaner 1 can autonomously travel and arrive at theposition of battery charger 9 basically without any guidance because itis configured to travel based on the map information stored in mapinformation storing section 28. Cleaner 1 is accessorily provided with asupersonic-wave sensor 29 for the guidance to the position of batterycharger 9. Supersonic-wave sensor 29 can receive a supersonic waveoutputted by the supersonic-wave generating unit 93. A receptionintensity of the supersonic wave in supersonic-wave sensor 29 isinputted to control unit 10. Control unit 10 can recognize if cleaner 1is approaching or moving away from battery charger 9 based a variationof the reception intensity of the supersonic wave in supersonic-wavesensor 29 during the traveling. In other words, the provision ofsupersonic-wave sensor 29 can lead cleaner 1 to reliably arrive at theposition of battery charger 9.

Cleaner 1 can start the cleaning operation when information for startingthe cleaning is inputted to input unit 25. Cleaner 1 can carry out thecleaning operation based on the inputted information, for example, thecleaning operation in accordance with the cleaning patterns for therespective rooms stored in map information storing section 28. Morespecifically, motor control unit 51 is driven so that cleaner 1 moves inaccordance with the cleaning patterns stored in map information storingsection 28, motor control units 52 and 53 are driven so that the dust israked up by main brush 72 and side brush 73, and motor control unit 64is driven so that the raked-up dust is sucked into the dust-collectingcup.

In cleaner 1, a timer operation in which the cleaning can start at adesignated time point can be optionally set. More specifically, wheninformation for designating the cleaning-start time is inputted to inputunit 25, cleaner 1 can commence the cleaning operation provided that thetime counted by timer 21 falls on the designated time.

Further, cleaner 1 can carry out a security operation other than thecleaning operation. More specifically, when information for designatinga time point when the security operation is implemented and a movingpattern is inputted to input unit 25, for example, cleaner 1 drivesmotor control unit 51 so as to move based on the designated movingpattern provided that the time counted by timer 21 falls on thedesignated time and carries out a cyclic operation. In implementing thesecurity operation, when the presence or movement of an object, a personor the like which is not usually anticipated is detected by proximitysensors 14 to 17 and/or distance-measuring sensors 11 to 13, cleaner 1can point camera 20 at the object or the person to thereby photograph itand transmit the captured image to a predetermined terminal disposeddistantly from cleaner 1 via communication unit 26 and antennas 18 and19.

In the embodiment so far described, in order for cleaner 1 to implementthe cleaning operation, the right and left drive wheels are driven forthe traveling, and main brush 72 and side brush 73 are rotated for thecleaning.

In order for the right and left drive wheels to be driven, a drivecurrent (hereinafter, referred to as traveling drive current) issupplied to left drive wheel motor 60 and right drive wheel motor 61under the controls of control unit 10 and motor control unit 51.

In order for main brush 72 and side brush 73 to be rotated, a drivecurrent (hereinafter, referred to as cleaning drive current) is suppliedto main brush motor 62 and side brush motor 63 under the controls ofcontrol unit 10 and motor control units 52 and 53.

In the case of cleaner 1 according to the present embodiment, membersconstituting the right and left drive wheels, main brush 72 and sidebrush 73 are selected so that the traveling drive current shows a valuebelow a value of the cleaning drive current.

As described, in cleaner 1, it is determined by determining section 46whether or not cleaner 1 is allowed to travel back to battery charger 9.In cleaner 1, when it is determined that cleaner 1 necessarily travelsback to battery charger 9, an arrangement is made in order to controlthe power consumption required for the traveling in surely returning tothe position of battery charger 9. When it is determined by determiningsection 46 that cleaner 1 is allowed to travel back to battery charger 9during the time when cleaner 1 is performing the cleaning operation, alength of time for applying the voltage supplied to left drive wheelmotor 60 and right drive wheel motor 61 per unit time is made shorterthan a length of time before then, in other words, a length of time inthe case in which the remaining volume of battery 30 is determined to beequal to or more than the sum of the battery volume required forreturning to the position of battery charger 9 and the predeterminedallowance volume. Thereby, the length of time for supplying the currentto left drive wheel motor 60 and right drive wheel motor 61 per unittime is shortened. The modes of controlling the voltage and the currentare described in detail referring to FIGS. 5A, 5B, 6A and 6B.

In cleaner 1, a PWM (Pulse Width Modulation) control is performed toleft drive wheel motor 60 and right drive wheel motor 61.

When the remaining volume of battery 30 is determined to be equal to ormore than the sum of the battery volume required for returning to theposition of battery charger 9 and the predetermined allowance volume,the voltage is applied to left drive wheel motor 60 and right drivewheel motor 61, for example, in a mode shown in FIG. 5A. Morespecifically, the control is performed in such manner that the voltageis applied (ON state) during 80% of unit time T and the application ofthe voltage is halted (OFF state) during 20% thereof, and the controlbased on the unit time T is continuously repeated.

When the remaining volume of battery 30 is determined to be less thanthe sum of the battery volume required for returning to the position ofbattery charger 9 and the predetermined allowance value, the voltage isapplied to left drive wheel motor 60 and right drive wheel motor 61, forexample, in a mode shown in FIG. 5B. More specifically, the control isperformed in such manner that the voltage is applied (ON state) during40% of the unit time T and the application of the voltage is halted (OFFstate) during 60% thereof, and the control based on the unit time T iscontinuously repeated.

When the voltage control as shown in FIG. 5A is performed, a currentcontrol as shown in FIG. 6A is performed to left drive wheel motor 60and right drive wheel motor 61 because battery 30 is the direct-currentpower supply. More specifically, the control is performed in such mannerthat the current is applied (ON state) during 80% of the unit time T andthe application of the current is halted (OFF state) during 20% thereof,and the control based on the unit time T is continuously repeated.

When the voltage control as shown in FIG. 5B is performed, a currentcontrol as shown in FIG. 6B is performed to left drive wheel motor 60and right drive wheel motor 61. More specifically, the control isperformed in such manner that the current is applied (ON state) during40% of the unit time T and the application of the current is halted (OFFstate) during 60% thereof, and the control based on the unit time T iscontinuously repeated.

Further, it is preferable that, in cleaner 1, a shortest path to batterycharger 9 be selected as a result of referencing map information storingsection 28 and/or a traveling path along a forward direction of acarpet, if the carpet is present in the traveling path, be selected inorder to reduce the power consumption required for cleaner 1 to travelback to battery charger 9. It is a possible option to further provide alight volume sensor, wherein cleaner 1 is returned to battery charger 9while auxiliary battery 32 is being charged by means of solar cell 33,and the path back to battery charger 9 is arranged to be a path in whicha light reception volume of solar cell 33 is increased based on adetection output of the light volume sensor in order to increase thecharge volume in charging auxiliary battery 32.

Further, cleaner 1 can be subjected to various modifications as shown inFIGS. 7 to 9. Hereinafter, a cleaner 100 shown in FIGS. 7 to 9 as amodification of cleaner 1 will be described referring the drawings.

Cleaner 100 includes, in place of antennas 18 and 19 provided in cleaner1, an incorporated antenna 18A housed in an inner side than outer jacket2.

Distance-measuring sensors 11 to 13 provided in cleaner 1 are omitted incleaner 100. In cleaner 100, a distance to an object is measured bysupersonic-wave sensor 29.

Further, cleaner 100 includes, in place of terrestrial magnetism sensor22 provided in cleaner 1, a gyro sensor 101. In cleaner 100, an angle atwhich cleaner 100 is rotated is measured by gyro sensor 101, whichserves to obtain an accurate angle even when any magnetized object suchas a steel pole is present in the vicinity of cleaner 100. In cleaners 1and 100, the function is utilized to accurately grasp the positionsthereof particularly on the carpet.

Further, cleaner 100 includes, in place of acceleration sensor 23provided in cleaner 1, a rotary encoder 102. Rotary encoder 102 includesa light emitting element and a light receiving element. A part of aright wheel or a left wheel of cleaner 100 is disposed between the lightemitting element and the light receiving element of rotary encoder 102.The part of the wheel serves to allow the light receiving element toreceive light emitted by the light emitting element at a predeterminedpattern for each rotation of the wheel. Accordingly, it is possible forrotary encoder 102 to detect the number of the rotations of the right orleft wheel in cleaner 100.

Further, in cleaner 100, a regulator 51A is connected between controlunit 10 and motor control unit 51. The power can be thereby supplied tomotor control unit 51 in a stable manner.

Although the present invention has been described and illustrated indetail, it is clearly understood that the same is by way of illustrationand example only and is not to be taken by way of limitation, the spiritand scope of the present invention being limited only by the terms ofthe appended claims.

1. A self-propelled cleaner comprising: a traveling unit; a travelingdrive unit for driving said traveling unit and allowing the cleaner toautonomously travel; a suction unit for implementing a suction operationfor cleaning, a power supply for supplying said traveling drive unit andsaid suction unit with a current; a control unit for controlling modesof supplying the current to said traveling drive unit and said suctionunit from said power supply; and a voltage detecting unit for detectinga voltage of said power supply, wherein when a voltage value detected bysaid voltage detecting unit is below a predetermined value, said controlunit makes a length of time for supplying said traveling drive unit withthe current within a predetermined length of time shorter than a lengthof time when the voltage value detected by said voltage detecting unitis equal to or more than said predetermined value.
 2. The self-propelledcleaner according to claim 1, wherein said power supply is connected toa battery charger to thereby serve as a rechargeable battery, thecleaner further comprises a path calculating section for calculating apath from a present position of said power supply to a position wheresaid battery charger is present, and said predetermined value is basedon a voltage value required for traveling the path calculated by saidpath calculating section.
 3. The self-propelled cleaner according toclaim 2, wherein said predetermined value is a sum of the voltage valuerequired for traveling the path calculated by said path calculatingsection and a predetermined allowance value.
 4. The self-propelledcleaner according to claim 3, wherein said control unit supplies saidtraveling drive unit with a current value lower than a current valuedemanded by said suction unit for the suction operation thereof in orderto drive said traveling unit.
 5. A self-propelled cleaner comprising: atraveling unit; a traveling drive unit for driving said traveling unitand allowing the cleaner to autonomously travel; a suction unit forimplementing a suction operation for cleaning, a power supply forsupplying said traveling drive unit and said suction unit with acurrent; and a control unit for controlling modes of supplying thecurrent to said traveling drive unit and said suction unit from saidpower supply, wherein said control unit supplies said traveling driveunit with a current value lower than a current value demanded by saidsuction unit for the suction operation thereof in order to drive saidtraveling unit.
 6. The self-propelled cleaner according to claim 5,wherein said power supply is connected to a battery charger to therebyserve as a rechargeable battery.
 7. A method of controlling aself-propelled cleaner comprising a traveling unit, a traveling driveunit for driving the traveling unit and allowing the cleaner toautonomously travel, a suction unit for implementing a suction operationfor cleaning, and a power supply for supplying said traveling drive unitand said suction unit with a current, the method comprising the stepsof: detecting a voltage of said power supply; determining whether or notthe voltage of said power supply is equal to or more than apredetermined value; supplying said traveling drive unit with thecurrent during a first length of time within a predetermined time lengthwhen the voltage of said power supply is equal to or more than thepredetermined value; and supplying said traveling drive unit with thecurrent during a second length of time shorter than the first length oftime within said predetermined time length when the voltage of saidpower supply is below the predetermined value.
 8. The method ofcontrolling the self-propelled cleaner according to claim 7, furthercomprising the step of: calculating a path from a present position ofsaid power supply to a position where said battery charger is present,wherein said predetermined value is based on a voltage value requiredfor traveling said calculated path in said determination step.